Conventional firearms primarily used for military and paramilitary purposes typically are either of a magazine fed type or an automatic belt fed type. For reasons of versatility and economy, it has been found to be desirable to be able to convert a magazine fed type of firearm into an automatic belt fed type of firearm. Accordingly, it is the principal object of the present invention to provide an attachment for converting a magazine fed firearm into an automatic belt fed firearm which is simple in design, comparatively inexpensive to manufacture and effective and reliable in performance.